The present invention relates to a method for the selective extraction of beta-lactoglobulin from whey or milk and other protein substances from whey. In particular the method consists in the extraction of beta-lactoglobulin from whey by means of subunit exchange chromatography and in the subsequent extraction of the other proteins by chromatography on a suitable ion exchange resin.
Whey, a by-product of the dairy industry, is a highly polluting liquid on account of its high content in protein substances at concentrations of ca 6 g/l.
Whey causes particularly difficult disposal problems on account of its remarkable volume.
On the other hand, the proteins contained in whey are products of potential industrial interest and of a high biological value. The recovery and isolation of these latter in a pure state by the use of economically acceptable methods can be considered an attractive aspect from the commercial view point.
For these reasons, methods have been recently developed for recovering proteins and other components of whey so as to make the latter less polluting (see: K. R. Marshall in "Developments in Dairy Chemistry" (K. K. Fox ed. 1982, Appl. Sci. Pub. London pages 339-373, I. Russell, Tibtech, 1986, 107-108).
The most common methods used so far enable one to obtain products, such as whey powder, whey concentrates, cheeses, such as curd or "Feta" cheese, which have a protein content generally of ca 10-15%.
Other more sophisticated methods, such as ultrafiltration, optionally coupled to absorption on ion exchange beds, permit obtaining protein mixtures, which are practically pure and in their native form (see: D. E. Palmer, Process Biochem., 1977, 12, pages 24-28).
In any case, however, the utilization of the whey proteins for specific end-uses, as, for instance, in the food industry in general, or in products for special diets, is to meet the double requirement of obtaining products with a high protein content and products in which the proteins are in their native form, i.e. with their functional properties intact.
The main component of the proteins of cow milk is beta-lactoglobulin, which constitutes 50% of the whey proteins.
Beta-lactoglobulin is also one of the major allergenic components of milk, particularly in infancy. A selective removal of said component could thus permit utilizing the remaining proteins for the production of dietetic hypoallergenic foodformulas of high additional value. Beta-lactoglobulin occurs in the form of two main genetic variants, named A and B and having a different electrophoretic mobility. It is a dimer of molecular weight 36 000; in the B variant the dimer undergoes a reversible monomerization at pH values in the range 1.8 to 5.2, the extent of which depends upon temperature. In the case of the A variant, such monomerization cannot be easily detected in the pH range 4.5 to 4.7, since the protein tends to polymerize into octamers.